Absence of Oxalobacter formigenes (Oxf) from the GI-tract is a risk factor for development of hyperoxaluria and calcium oxalate kidney stones. Recent data now indicate that patients with recurrent urolithiasis have a lower prevalence rate of Oxf in their stools than non-stone forming individuals. In addition, urinary oxalate levels are higher in non-colonized individuals as compared to colonized individuals. This indicates a clinical need for a test that can identify non-colonized individuals. Phase I of this grant resulted in the development of a reliable and rapid PCR ELISA-based microtiter plate assay for the detection of Oxf in human fecal samples. Pre-clinical performance data for the test (Le. its analytical sensitivity, analytical specificity, precision and reproducibility) were obtained as per the NCCLS guidelines. In Phase II of this project, we propose to complete the development of a production prototype of the XEntrix(TM) O. formigenes Monitor Kit. Analytical and clinical performance of the prototypic test kit will be determined in a multicentre clinical trial. The clinical studies have been designed not only to validate the test kit but also to strengthen the utility of Oxf determination as a diagnostic tool for the assessment of risk for calcium oxalate urolithiasis. By end of the proposed Phase II studies, we will have sufficient analytical and clinical performance data on this diagnostic kit to seek a pre-market approval under section 510K of the Food Drugs and Cosmetic Act, from the Center for Devices and Radiological Health.